1. Field of the Invention
The present invention relates to molded connection or terminal portions of cross-linked polyethylene insulated cables.
2. Description of the Prior Art
To form molded connections for cross-linked polyethylene insulated cables, known methods generally comprise subjecting a polyethylene tape to electron beam irradiation to effect cross-linking, winding the irradiated polyethylene tape around a cable and then heat molding the resulting assembly. The use of irradiated polyethylene which has been subjected to partial cross-linking permits satisfactory molding since no eccentricity, deformation or the like is caused by heating, and the initial breaking or separation characteristics of the molds are superior as compared with the use of uncross-linked polyethylene. On the other hand, complete fusion between layers of the tape or between the tape and the cable insulators cannot be expected by this method. As a result, after long times under high temperature, in particular after immersion in water for long times under an applied voltage, those portions which are not completely fused some time produce water trees (or electrochemical trees, as they are sometimes termed) to cause dielectric breakdown.
Most particularly, foreign particles wound between layers of tape tend to form nuclei around which water trees develope into the tapes remarkably.